Lumbar Facet Arthropathy


KEY FACTS

Terminology

  • Facet arthrosis, degenerative facet disease, degenerative joint disease, facet hypertrophy

  • Osteoarthritis of synovially lined lumbar apophyseal joints

Imaging

  • Osseous overgrowth impinging on foramina in conjunction with articular joint space narrowing

    • Mushroom cap facet appearance

    • Joint space narrowing with sclerosis/bone eburnation, ligamentum flavum hypertrophy

    • Intraarticular gas, effusion

    • Spondylolisthesis not uncommon

  • CT more sensitive than plain films for detecting presence and degree of arthrosis

    • Facet hypertrophic degenerative arthropathy, particularly superior articular facet extending into lumbar foramen

  • MR best demonstrates degenerative facet compression of thecal sac and fat-filled neural foramina

    • Enhancing inflammatory soft tissue changes surrounding facet joint not uncommon

  • Consider CT myelography if MR contraindications or MR does not demonstrate facet relationship to neural foramina

Top Differential Diagnoses

  • Septic facet

  • Inflammatory arthritides

  • Paget disease

  • Tumor

    • Metastasis

    • Lymphoma

Diagnostic Checklist

  • Look for associated synovial cysts

Lateral radiograph shows facet hypertrophy and bony eburnation of the L4-L5 and L5-S1 facets
.

Sagittal T1WI MR shows L4-L5, L5-S1 facet degenerative arthropathy with bony hypertrophy and low signal involving the facets from bony sclerosis
. There is narrowing of the L5-S1 foramen
primarily by the hypertrophied superior articular facet of S1.

Axial bone CT shows severe left unilateral facet overgrowth
, causing moderately severe central stenosis
. The facet overgrowth has been described as having a mushroom cap appearance.

Axial T1WI MR shows marked facet hypertrophic degenerative arthropathy with enlarged facets
, producing moderately severe foraminal stenosis
.

TERMINOLOGY

Synonyms

  • Facet arthrosis, degenerative facet disease, degenerative joint disease, facet hypertrophy

Definitions

  • Osteoarthritis of synovially lined lumbar apophyseal joints

IMAGING

General Features

  • Best diagnostic clue

    • Osseous facet overgrowth impinging on neural foramina in conjunction with articular joint space narrowing

  • Location

    • Facet joints of lumbar spine

  • Size

    • Minimal → large osteophytes approximating size of facet themselves

  • Morphology

    • Osseous facet overgrowth and cartilage erosion with joint space narrowing

Radiographic Findings

  • Radiography

    • Poor for mild facet degeneration, severe well demonstrated

    • Oblique views demonstrate facet joints best

      • “Mushroom cap” facet appearance

      • Joint space narrowing with sclerosis/bone eburnation

      • Intraarticular gas (“vacuum phenomenon”)

      • Spondylolisthesis not uncommon

Fluoroscopic Findings

  • Same as plain radiography; can observe motion abnormalities on flexion/extension

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